Carboxylate anions benzoate

Fersht and Kirby, 1968b. Formation of the anhydride is rate determining here. The reference reaction is that of phenyl acetate with a carboxylate anion of pK, 3.11 (see note a) y Kemp and Thibault, 1968. The reference reaction is that of RCOO- with phenyl benzoate (see note j)... 

A few mixed compounds of Eu3+ containing dibenzoylmethide ion and carboxylate anions (acetate, propionate and benzoate) of the general formula, (DBM)2EuOCOR, have been isolated [43Z], Thermogravimetric investigations on these complexes show that their heat stability decreases in the order acetate > propionate > benzoate. The melting points of... 

Molecules 20-22 in which a ferrocene-lj -bisamide is bridged across the upper rim of a calix[4]arene show interesting anion sensing selectivity [19]. The results of H NMR studies in CD3CN show that the receptors preferentially bind carboxylate anions (acetate and benzoate) over dihydrogenphosphate and chloride. 

Carboxylates as the phenylacetate anion also eject electrons in methanol [75] giving benzyl anion after recombination between solvated electron and benzyl radical [76]. In phenyl substituted carboxylate anions (from benzoate to phenylbutyrate) in water the quantum yield of photoejected electron was found between 0.002 and 0.03 these values increase with increasing excitation energy and with the number of CH2 separating the phenyl and carboxylate group [77], In the case of phenylalanine and tryptophan in water, the mechanism seems to differ according to the conditions biphotonic and from a triplet state in neutral solution or monophotonic in basic medium [78, 79, 80]. In certain cases, the quantum yield for electron ejection is found to increase with pH [79], The anion of bromouracil also gives hydrated electron [81]. 

Since coordinatively unsaturated Zn polyamine complexes display a good affinity towards the COO group, the [Zn (42)] + platform was first tested for fluorescent sensing of carboxylate anions. For instance, there is evidence from spec-trophotometric titration experiments that [Zn (42)] + forms a stable adduct with benzoate, in ethanolic solution at 25 °C. However, even after the addition of a large excess of benzoate to an ethanolic solution of [Zn (42)] +, the typical fluorescent emission of the anthracene fragment is not altered at all. Quite interestingly, when a solution of [Zn (42)] " is titrated with the 4-A,JV-dimethylamine-benzoate anion, the anthracene emission is progressively quenched the fluorescence intensity, Ip, versus anion equivalents profile corresponds to the formation of a T. 1 adduct, and... 

Stability constants were obtained for receptors 13a, 13b and 13c using analogous conditions to those employed for receptors 12a, 12b and 12c. As with the pyridine-2,6-dicarboxamide macrocydes, the stability constants for the isophthalamide macrocydes appear to be influenced by the size and flexi-bihty of the system with the higher constants observed in the 20-membered receptor 13a with notable decreases in the assodation constants with the 22-and 24-membered receptors 13b and 13c. The greatest decreases where observed in the stability constants obtained with the carboxylate anions. In the case of acetate the constants decreased from 3130 M for 13a to 552 M and 205 M for 13b and 13c, respedively. hi the case of benzoate a constant of 601 M was calculated for 13a decreasing to 302 M and 82 M for 13b and 13c, respectively. Unexpectedly lower binding constants were obtained for the isophthalamide macrocydes (13a-13c) compared to the pyridine-... 

Sessler and co-workers have incorporated two carbazole subunits into expanded calixpyrrole-type macrocycle 53 [71]. Fluorescence titration experiments in dichloromethane at 0.5 iM concentration of host revealed that compound 53 shows selectivity for acetate (fCa = 229 000 M ) over a number of other carboxylate-type anions (benzoate, oxalate and succinate). 

Carboxylic AcidPerivatives. Detailed investigations into the electrolytic reduction of carboxylic acid derivatives (esters, anhydrides, amides) in nonaqueous solutions and the procedures for producing the respective radical anions have been described in the report by iDyasov and his co-workers f39]. They obtained radical anions from esters of aromatic carboxylic acids (benzoates, phtha-lates, isophthalates) and from phthalic anhydride and analyzed their EPR spectra. The production of radical anions of acrylates and methacrylates by electrochemical generation and the effect of proton donors on their stability was also described [11]. 

As discussed above (Section 66.3), phenacyl ester radical anions fragment readily to phenacyl radicals and carboxylate anions. The radical anions of benzoate esters also fragment to carboxylate anions and alkyl radicals, and this process is faster if the alkyl radical is stabilized (3°, benzyhc). This concept has been applied successfully to the deoxygenation of carbohydrate alcohols by photoinduced electron transfer (PET) sensitization. For instance, irradiation of 38 in water/2-propanol, using a substituted... 

Many of these salts melt or sublime before or during decomposition and reaction temperatures generally increase with molar mass. Thermal analyses for a selection of ammonium carboxylates have been given by Erdey et al. [915] who conclude that the base strength of the anion increases with temperature until it reaches that of NH3. Decompositions of ammonium acetate (>333 K) and ammonium oxalate (>473 K) proceed through amide formation. Ammonium benzoate and ammonium salicylate sublime (>373 K) without decomposition but ammonium citrate decomposes (>423 K) to yield some residual carbon. 

The name of a carboxylic acid always ends in -ic, and the name of the anion ends in -ate. Figure 17-9 shows three simple carboxylic acids formic acid ( K = 1.8 x 10 ), acetic acid ( K — 1.8 X 10 ), and benzoic acid ( Ta = 6.4 X 10 ). HCO2 is formate, CH3 CO2 is acetate, and Cg H5 CO2 is benzoate. Examples and treat benzoic acid quantitatively. 

LDHs are also promising materials as sorbents for anionic organic contaminants via both ion-exchange and reconstruction reactions. There have been a large number of reports of the use of LDHs for removal of species such as aromatic carboxylic acids, phenols, pesticides, and humic or fulvic acids. Recently, Cardoso et al. [152] found that the sorption process of terephthalate anions from aqueous solutions by calcined Mg/Al - CO3 LDHs takes place by reconstruction of the LDHs and involves the intercalation and adsorption of terephthalate anions. Calcined Mg/Al - CO3 LDHs were found to be capable of removing 40 to 85 % of the benzoate from solutions in the concentration... 

Upon m-xylene oxidation, the above band of m-tolualdehyde disappears near 523 K, while a couple of strong and broad bands is grown near 1530 and 1430 cm. These bands are typical of carboxylates and are again observed, with very weak band shifts, upon oxidation of all methyl-benzenes, as well as of the corresponding aromatic aldehydes. They can be assigned predominantly (if not entirely) to benzoate and toluate anions (28) (in Figure 2, meta-toluate anions). These bands raise their maximum near 523 K in all cases and suddenly disappear above 673 K, when gas-phase CO2 begins to be detectable. 

While high polymers of /3-lactones can also be formed by cationic polymerization, most of the commercial production seems to be by the anionic route. Carboxylate salts such as sodium acetate or benzoate are commonly the initiators, but other nucleophiles, such as triethylamine, betaine, potassium f-butoxide, aluminum and zinc alkoxides, various metal oxides and tris(dimethylamino)benzylphosphonium chloride (the anion of which is the initiator), are of value. Addition of crown ethers to complex the counter cation increases the rate of reaction. When the reaction is carried out in inert but somewhat polar organic solvents, such as THF or ethyk acetate, or without solvent, chain propagation is very fast and proceeds without transfer reactions. 

Tetrahedral tetraazonium compounds 5a and 5b, developed by Schmidt-chen, bind carboxylates, such as formiate, acetate, and benzoate, among a variety of other anions [8]. Although these receptors do not display hydrogen bond interactions, they are endowed with well localized polycationic centers, which are independent on the acidity of the medium. A ditopic receptor build up of both a 5a and a 5b subunits bridged by a p-xylylene spacer showed selectivity towards the largest members of a series of dianionic probes [9],... 

In the presence of a large excess of EtO ion, the bimetallic catalyst is fully saturated with EtO as shown by structure I in Scheme 5.3. Incremental additions of a carboxylate substrate would cause the gradual conversion of I into the 1 1 productive complex II, but further additions would yield the unproductive complex III. As expected from this mechanism a bell-shaped profile is observed in a plot of initial rate versus substrate concentration related to the catalyzed ethanolysis of 16 (Figure 5.5). The fairly good quality of the fit supports the validity of Scheme 5.3. Further confirmation comes from the finding that benzoate anions behave as competitive inhibitors of the reaction. Since the reaction product of the ethanolysis of 16 is also a benzoate anion, product inhibition is expected. Indeed, only four to five turnovers are seen in the ethanolysis of 16 before product inhibition shuts down the reaction. The first two turnovers are shown graphically in Figure 5.6. 

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